What would cause a 5 1/4 Floppy drive to work fine in Windows but not DOS? \ VOGONS

What would cause a 5 1/4 Floppy drive to work fine in Windows but not DOS?

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First post, by Digitoxin

Posted on 2022-02-24, 04:08

Digitoxin Offline

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I have a Core 2 Duo machine that I use for running legacy software and backing up my floppy disk collection. it was one of the last platforms to support floppy drives, but it only supports a single drive. I currently have a 5 1/4 drive installed in it. I'm using the machine to make backups of my floppy disk game collection. For most of the disks, I use Winimage and call it a day, but I have several old Sierra AGI games with disk based copy protection I would like to remove so I can use the games in DOSBox.

I have a tool to remove the copy protection, but it runs in DOS and requires the original disk (which I have) to work. I have a hard drive formatted with DOS 6.22 installed for this purpose. However, when I boot into DOS, floppy disks are unreadable in the 5 1/4 drive even though the drive works fine in Windows.

Is this a timing issue with the 5 1/4 drive because the machine is too new or is this an issue of bad or insufficient BIOS support for 5 1/4 drives? If I connect a 3 1/2 drive to the machine, it works fine in both DOS and Windows.

If its a platform compatibility issue and I want to put together an older machine, how far back to I need to go to guarantee compatibility with the 5 1/4 drive in DOS?

Edit: just to be clear since some of these keep coming up.

1. My motherboard only supports a single floppy drive at a time. I only have one floppy drive connected. I am not trying to connect more than one floppy drive to the system.
2. The drive is connected to the correct header on the cable.
3. I have tried swapping the cable and am currently using a brand new cable.
4. It is a 1.2M floppy drive and is correctly configured as such in the BIOS
5. I have connected a 3 1/2 floppy drive and that drive works properly in both Windows and DOS. Only the 5 1/4 drive will not read in DOS.
6. When trying to access a 5 1/4 floppy in DOS, it tries to read the disk but immediately comes back with General failure reading drive A.
7. I have tried reading both 360K and 1.2M floppies in DOS. Both give me the same error. These disks read fine in Windows.
8. I am using Windows XP when booting in Windows. I have not tried installing and trying Windows 95 or 98. I figured the platform was too new to bother.
9. I have a feeling the BIOS does not correctly support 5 1/4 floppy drives even though the option exists to choose one in the BIOS. I'm pretty sure Windows XP and later bypass the BIOS and access the floppy controller directly.

Last edited by Digitoxin on 2022-02-25, 00:54. Edited 4 times in total.

Reply 1 of 9, by BitWrangler

Posted on 2022-02-24, 04:13

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Some BIOS of newer machines only support drive A: so if that's the case, DOS doesn't see what BIOS doesn't see... I believe there may be incantations like drvparm arguments to summon it into DOS's presence but the deep magic leaks out of the sorcerers brain unless used, so I can't recall much detail right now.

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Reply 2 of 9, by rmay635703

Posted on 2022-02-24, 05:01

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Before twist or after?
Could be in the cable position for drive B

Or you might have a drive old enough to have configuration jumpers putting it to the wrong number

Reply 3 of 9, by Digitoxin

Posted on 2022-02-24, 07:48

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Its connected properly as drive A. When trying to read any disks in DOS, it attempts to read the disk, but I get General failure reading drive A. I have no issue reading the same disks when in Windows.

Reply 4 of 9, by Doornkaat

Posted on 2022-02-24, 07:53

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This may sound dumb but you did configure the drive as a 1.2MB floppy in BIOS, right?

Reply 5 of 9, by Deunan

Posted on 2022-02-24, 09:00

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Yup, that looks like a bad drive type selected in BIOS. Windows probably checks the first sector and uses media code to set the expected format parameters. DOS on the other hand has these params hardwired and selected during boot based on BIOS settings.

Reply 6 of 9, by Digitoxin

Posted on 2022-02-24, 23:48

Digitoxin Offline

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The drive is configured correctly in the BIOS. It is a 1.2M Floppy drive and is configured as such. I can read and write both 360K and 1.2M floppies fine in Windows. In DOS, if I try to access any disk in the drive I get a General failure reading drive A error.

I have tried both MS-DOS 6.22 and FreeDos. Both have the same issue.

If I disconnect the 5 1/4 drive and connect a 3 1/2 drive instead, that drive is readable in both DOS and Windows. It is only the 5 1/4 drive that is having the issue.

I also replaced the floppy cable in case it was an issue with a bad cable. The cable I am currently using is brand new.

Reply 7 of 9, by Errius

Posted on 2022-02-25, 00:31

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I have encountered this problem twice:

First, with an old 440FX system. The floppy worked in Windows NT 4.0 but not in DOS or at POST. It turned out the motherboard floppy controller was failing. I wound up swapping the motherboard.

Second, a Pentium 4 system. Again the floppy drive works in Windows but not in DOS. Swapping the floppy drive/cable makes no difference. USB floppy drive works well (with integrated floppy controller disabled in BIOS). Cloning the MS-DOS partition to a USB drive, then booting from the USB drive, also eliminates the problem. I still haven't figured out what is causing this.

The drives in both cases are 3.5" HD

BitWrangler wrote on 2022-02-24, 04:13:
Some BIOS of newer machines only support drive A: so if that's the case, DOS doesn't see what BIOS doesn't see...

The OP should consider reflashing the BIOS. If the problem persists maybe try an older BIOS.

Is this too much voodoo?

Reply 8 of 9, by cyclone3d

Posted on 2022-02-25, 01:59

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You could try a parallel port floppy drive if you can get a parallel port card that will work in DOS with that machine.

As far as how far you would have to go back for full support of a 1.2M drive, I would think that anything that has support for 2 floppy drives in the BIOS should work fine

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Reply 9 of 9, by Horun

Posted on 2022-02-25, 04:12

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Yep, Yep, Yep... if the motherboard is soc478 or newer and only supports one floppy then in DOS it may never support a 1.2Mb drive without driver support if it has a odd OEM BIOS.
What motherboard is it ? You never mentioned it and that can lead to the solution....
I have a Compaq board (with odd Pheonix BIOS) that acts that way, only supports 1.44Mb drives but BIOS allows choosing a 1.2MB or 1.44Mb but for some reason Windows sees it proper....

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

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